They believe the group charged them each €20,000 in return for passports and other documents forged in China.

Once in Europe, they were housed in Barcelona and other Catalan towns until they received new forged documents, which were sent via courier companies once a week. Plane tickets were bought with budget airlines on the day of the flight to avoid police detection.

‘Passers’ and ‘teachers’ were also supplied to accompany the trafficked persons throughout the trip and coach them in commonly-used phrases in border control.

The human trafficking ring was discovered after five migrants agreed to give evidence and enter the witness protection programme.

The 155 people arrested are mostly of Chinese nationality and police believe four of those arrests are gang leaders. 111 of the arrests were made at El Prat de Llobregat Airport in Barcelona.